Bonding Structure with Stress Buffer Zone and Method of Forming Same
A method includes depositing a first dielectric layer on a first substrate of a first device die, etching the first dielectric layer to form a trench, depositing a metallic material in the trench and on a top surface of the first dielectric layer, and performing a chemical mechanical polish (CMP) process to remove a portion of the metallic material from the top surface of the first dielectric layer to form a first metal pad. After the performing of the CMP process, the method selectively etches the first metal pad to form recesses at an edge portion of the first metal pad, deposits a second dielectric layer on a second substrate of a second device die, forms a second metal pad in the second dielectric layer, and bonds the second device die to the first device die.
This claims the benefits to U.S. Provisional Application Ser. No. 63/357,092 filed Jun. 30, 2022 and U.S. Provisional Application Ser. No. 63/382,138 filed Nov. 3, 2022, the entire disclosures of which are incorporated herein by reference.
BACKGROUNDThe semiconductor integrated circuit (IC) industry has experienced exponential growth. Technological advances in IC materials and design have produced generations of ICs where each generation has smaller and more complex circuits than the previous generation. In the course of IC evolution, functional density (i.e., the number of interconnected devices per chip area) has generally increased while geometry size (i.e., the smallest component (or line) that can be created using a fabrication process) has decreased. This scaling down process generally provides benefits by increasing production efficiency and lowering associated costs. Such scaling down has also increased the complexity of processing and manufacturing ICs.
For example, packages of integrated circuits are becoming increasingly complex, with more device dies packaged in the same package to achieve more functions. System-on-integrate-chip (SoIC) has been developed to include a plurality of device dies such as processors and memory cubes in the same package. The SoIC can include device dies formed using different technologies and have different functions bonded to the same device die, thus forming a system. This may save manufacturing cost and optimize device performance. To bond device dies together, two metal pads are pressed against each other at an elevated temperature, and the inter-diffusion of the metal pads causes the bonding of the metal pads. Coefficients-of-thermal-expansion (CTEs) mismatches between metal pads and surrounding dielectric layers may weaken bonding strength. Therefore, there is a need to further develop bonding structures to address these concerns with enhanced circuit performance and reliability.
The present disclosure is best understood from the following detailed description when read with the accompanying figures. It is emphasized that, in accordance with the standard practice in the industry, various features are not drawn to scale and are used for illustration purposes only. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.
The following disclosure provides many different embodiments, or examples, for implementing different features of the invention. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact.
In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. Moreover, the formation of a feature on, connected to, and/or coupled to another feature in the present disclosure that follows may include embodiments in which the features are formed in direct contact, and may also include embodiments in which additional features may be formed interposing the features, such that the features may not be in direct contact. In addition, spatially relative terms, for example, “lower,” “upper,” “horizontal,” “vertical,” “above,” “over,” “below,” “beneath,” “up,” “down,” “top,” “bottom,” etc. as well as derivatives thereof (e.g., “horizontally,” “downwardly,” “upwardly,” etc.) are used for ease of the present disclosure of one features relationship to another feature. The spatially relative terms are intended to cover different orientations of the device including the features. Still further, when a number or a range of numbers is described with “about,” “approximate,” and the like, the term is intended to encompass numbers that are within +/−10% of the number described, unless otherwise specified. For example, the term “about 5 nm” encompasses the dimension range from 4.5 nm to 5.5 nm.
The present disclosure provides various embodiments of system-on-integrate-chip (SoIC) packages and the method of forming the same. Particularly, a bonding structure with stress buffer zone (or stress release zone) is provided. Some variations of some embodiments are discussed. Throughout the various views and illustrative embodiments, like reference numbers are used to designate like elements. The intermediate stages of forming SoIC packages are illustrated in accordance with some embodiments. It is appreciated that although the formation of SoIC packages is used as examples to explain the concept of the embodiments of the present disclosure, the embodiments of the present disclosure are readily applicable to other bonding methods and structures in which metal pads and vias are bonded to each other.
Illustrated in
The method 10 at operation 12 (
The substrate 102 may be a semiconductor substrate, such as a bulk semiconductor, a semiconductor-on-insulator (SOI) substrate, a semiconductor wafer, or the like, which may be doped (e.g., with a p-type or an n-type dopant) or undoped. Generally, a SOI substrate includes a layer of a semiconductor material formed on an insulator layer. The insulator layer may be, for example, a buried oxide (BOX) layer, a silicon oxide layer, or the like. The insulator layer is provided on a substrate, typically a silicon substrate or a glass substrate. Other substrates, such as a multi-layered or gradient substrate may also be used. In some embodiments, the semiconductor material of the substrate may include silicon; germanium; a compound semiconductor including silicon carbide, gallium arsenic, gallium phosphide, indium phosphide, indium arsenide, and/or indium antimonide; an alloy semiconductor including SiGe, GaAsP, AlInAs, AlGaAs, GaInAs, GaInP, and/or GaInAsP; or combinations thereof.
In some embodiments, the substrate 102 and features formed thereon are used to form a device die, integrated circuit die, or the like. In the depicted embodiment, integrated circuit device region(s) 106 is formed on the top surface of the substrate 102. Exemplary integrated circuit devices may include complementary metal-oxide semiconductor (CMOS) transistors, fin field-effect transistors (FinFETs), resistors, capacitors, diodes, the like, or a combination thereof. The details of the integrated circuit devices are not illustrated herein. In other embodiments, the substrate 102 is used for forming an interposer structure. In such embodiments, no active devices such as transistors are formed on the substrate 102. Passive devices such as capacitors, resistors, inductors, or the like may be formed in the substrate 102. The substrate 102 may also be a dielectric substrate in some embodiments in which the substrate 102 is part of an interposer structure. In some embodiments, through vias (not shown) may be formed extending through the substrate 102 in order to interconnect components on the opposite sides of the substrate 102.
The method 10 at operation 14 (
Contact plugs 110 are formed in the ILD layer 108, and are used to electrically connect integrated circuit devices to overlying metal lines and vias. In some embodiments, the contact plugs 110 are formed of a conductive material selected from tungsten, aluminum, copper, titanium, tantalum, titanium nitride, tantalum nitride, alloys therefore, and/or multi-layers thereof. The formation of the contact plugs 110 may include forming contact openings in the ILD layer 108, filling a conductive material(s) into the contact openings, and performing a planarization (such as chemical mechanical polish (CMP) process) to level the top surfaces of the contact plugs 110 with the top surface of the ILD layer 108.
The interconnect structure 112 provides routing and electrical connections between devices formed in the substrate 102, and may be, e.g., a redistribution structure or the like. The interconnect structure 112 may include a plurality of insulating layers 114, which may be inter-metal dielectric (IMD) layers. Each of the insulating layers 114 includes conductive features, such as metal lines 116 and vias 118 formed therein in a metallization layer. In other embodiments, the metal lines may be, for example, redistribution layers. The conductive features may be electrically connected to the active and/or passive devices of the substrate 102 by the contact plugs 110.
The conductive features of the interconnect structure 112 that are formed in the topmost insulating layer 114 are separately labeled as metal pads 120 in
In some embodiments, the insulating layers 114 may be formed from a low-k dielectric material having a k-value lower than about 3.0. The insulating layers 114 may be formed from an extra-low-k (ELK) dielectric material having a k-value of less than 2.5. In some embodiments, the insulating layers 114 may be formed from an oxygen-containing and/or carbon containing low-k dielectric material, Hydrogen SilsesQuioxane (HSQ), MethylSilsesQuioxane (MSQ), the like, or a combination thereof. In some embodiments, some or all of insulating layers 114 are formed of non-low-k dielectric materials such as silicon oxide, silicon carbide (SiC), silicon carbonitride (SiCN), silicon oxycarbonitride (SiOCN), or the like. In some embodiments, etch stop layers (not shown), which may be formed of silicon carbide, silicon nitride, or the like, are formed between insulating layers 114. In some embodiments, the insulating layers 114 are formed from a porous material such as SiOCN, SiCN, SiOC, SiOCH, or the like, and may be formed by spin-on coating or a deposition process such as plasma enhanced chemical vapor deposition (PECVD), CVD, PVD, or the like. In some embodiments, the interconnect structure 112 may include one or more other types of layers, such as diffusion barrier layers (not shown).
In some embodiments, the interconnect structure 112 may be formed using a single and/or a dual damascene process, a via-first process, or a metal-first process. In an embodiment, an insulating layer 114 is formed, and openings (not shown) are formed therein using acceptable photolithography and etching techniques. Diffusion barrier layers (not shown) may be formed in the openings and may include a material such as TaN, Ta, TiN, Ti, CoW, or the like, and may be formed in the openings using a deposition process such as CVD, Atomic Layer Deposition (ALD), or the like. A conductive material may be formed in the openings from copper, aluminum, nickel, tungsten, cobalt, silver, combinations thereof, or the like, and may be formed over the diffusion barrier layers in the openings using an electro-chemical plating process, CVD, ALD, PVD, the like, or a combination thereof. After formation of the conductive material, excess conductive material may be removed using, for example, a planarization process such as CMP, thereby leaving conductive features in the openings of the respective insulating layer 114. The process may then be repeated to form additional insulating layers 114 and conductive features therein. In some embodiments, the topmost insulating layer 114 and the metal pads 120 formed therein may be formed having a thickness greater than a thickness of the other insulating layers 114 of the interconnect structure 112. In some embodiments, one or more of the topmost conductive features are dummy metal lines or dummy metal pads 120 that are electrically isolated from the substrate 102.
The method 10 at operation 16 (
The method 10 at operation 18 (
In some embodiments, the conductive pads 124 that are electrically connected to the interconnect structure 112 may be used as test pads before additional processing steps are performed. For example, the conductive pads 124 may be probed as part of a wafer-acceptance-test, a circuit test, a Known Good Die (KGD) test, or the like. The probing may be performed to verify the functionality of the active or passive devices of the substrate 102 or the respective electrical connections within the substrate 102 or interconnect structure 112. The probing may be performed by contacting a probe needle 126 to the conductive pads 124. Therefore, the conductive pads 124 may also be referred to as probe pads 124. The probe needle 126 may be a part of a probe card that includes multiple probe needles 126 which, for example, may be connected to testing equipment.
The method 10 at operation 20 (
The method 10 at operation 22 (
The method 10 at operation 24 (
The method 10 at operation 26 (
The method 10 at operation 28 (
The method 10 at operation 30 (
The first wet cleaning process may be performed by using a cleaning solution. An exemplary cleaning solution includes an ozone in deionized water (O3/DI) cleaning solution or a SPM cleaning solution. The SPM cleaning solution includes a mixture of sulfuric acid, a hydrogen peroxide solution, and pure water. The metal oxides and other remaining residues are removed from the frontside of the device structure 100 the first wet cleaning process.
The second wet cleaning process may be a selective wet etching process with a suitable etching solution. The second wet cleaning process uses an etching solution different from the first wet cleaning process. The etching solution may be an alkaline solution or an acid solution. An exemplary etching solution includes a mixture of methane, sulfinylbis(methane), hydroxylamine, and water. The etching solution has a selectivity of the bonding metal to the bonding dielectric layer from about 30:1 to about 100:1, such that the dielectric material of the dielectric layer 134 surrounding the bonding metal suffers insignificant etching loss. The etching solution may be applied for a duration of about 10 seconds to about 150 seconds.
A region 159 in
Referring to
In various embodiments, the recesses 160 allow some space for the expansion of the metallic materials during thermal cycles (such as the pre-anneal and anneal). The stress suffered by the bonded structure is thus reduced. In the illustrated embodiment, the selective etching process in forming the recesses 160 is performed after the singulation process at operation 28. In alternative embodiments, the selective etching process in forming the recess 160 may be performed prior to the singulation process at operation 28, such as after the planarization process at operation 26 and prior to the deposition of the patterned resist layer 154 and the attaching of the frame 150. A separate wet cleaning process may be performed after operation 28 to remove the remaining particles of the patterned resist layer 154 and metal oxides from the bond pads 148.
The method 10 at operation 32 (
The method 10 at operation 34 (
Similar to the device structure 100, the device structure 200 includes a substrate 202, integrated circuit device region(s) 206, an interconnect structure 212 that includes metal lines 216 and vias 218 embedded in insulating layers, and metal pads 220. The material compositions and formation of the substrate 202, the integrated circuit device region(s) 206, interconnect structure 212, the metal pads 220, the adhesive layer 252, the frame 250, and the patterned resist layer 254 may be substantially similar to the substrate 102, the integrated circuit device region(s) 106, the interconnect structure 212, the metal pads 120, the adhesive layer 152, the frame 150, and the patterned resist layer 154 as discussed above, respectively, which are not repeated herein for the sake of simplicity. After the singulation of the device structures 200, the patterned resist layer 254 is subsequently removed using, for example, a suitable ashing or stripping process, such as using an oxygen plasma or the like.
In the depicted embodiment, through vias 228 are formed in the substrate 202. In some embodiments, the through via 228 may also be termed through-silicon-via when the substrate 202 is a silicon-containing substrate. In some embodiments, the through vias 228 extend into the substrate 202 and will be exposed from a backside of the substrate 202 after a backside grinding process. In other words, the through vias 228 may extend between two opposite surfaces of the substrate 202. The through vias 228 may also be referred to as through-substrate-vias (TSVs). In some embodiments, the TSVs 228 include copper, a copper alloy, aluminum, an aluminum alloy or a combination thereof. In some embodiments, the TSVs 228 further includes a diffusion barrier layer (not shown) between the conductive via and the substrate 202. The diffusion barrier layer may include Ta, TaN, Ti, TiN, CoW or a combination thereof.
The method 10 at operation 36 (
The method 10 at operation 38 (
The method 10 at operation 40 (
At the conclusion of operation 40, the method 10 may perform a surface treatment process to the device structure 200. The surface treatment may include a first wet cleaning process similar to the first wet cleaning process in the surface treatment process 158 discussed above, which removes residues and metal oxides from the backside of the device structure 200. Optionally, the surface treatment may also include a second wet cleaning process (or selective etching process) similar to the second wet cleaning process in the surface treatment process 158 in forming recess rings encircling the bond pads 248. Formation of recesses at edge portions of the bond pads 248 in the device structure 200 may be skipped, in some embodiments. Alternatively, recesses at edge portions of the bond pads 248 may be formed in the device structure 200, but skipped in the device structure 100. That is, the device structure 100 and the device structure 200 may either have the recesses encircling respective bond pads, or both, in accordance with some embodiments.
The method 10 at operation 42 (
To achieve the hybrid bonding, the device structure 200 are first pre-bonded to the device structure 100 by lightly pressing the device structure 200 against the device structure 100. After pre-bond, an anneal is performed to cause the inter-diffusion of the metals in the bond pads 148 and the corresponding overlying bond pads 248. The annealing temperature may be in the range between about 250° C. and about 550° C. in some embodiments. The annealing time may be in the range between about 1.5 hours and about 8.0 hours in some embodiments. Through the hybrid bonding, the bond pads 248 are bonded to the corresponding bond pads 148 through direct metal bonding caused by metal inter-diffusion.
A region 259 in
The method 10 at operation 44 (
A region 278 in
The method 10 at operation 46 (
The embodiments of the present disclosure have some advantageous features. By forming recesses encircling bond pads, stress in the bonded structures is reduced, particularly in thermal cycles. The reliability of the bonded structure is thus improved.
In one exemplary aspect, the present disclosure is directed to a method. The method includes depositing a first dielectric layer on a first substrate of a first device die; etching the first dielectric layer to form a trench; depositing a metallic material in the trench and on a top surface of the first dielectric layer; performing a chemical mechanical polish (CMP) process to remove a portion of the metallic material from the top surface of the first dielectric layer, wherein a remaining portion of the metallic material in the trench forms a first metal pad; after the performing of the CMP process, selectively etching the first metal pad to form recesses at an edge portion of the first metal pad; depositing a second dielectric layer on a second substrate of a second device die; forming a second metal pad in the second dielectric layer; and bonding the second device die to the first device die, wherein the second dielectric layer is bonded to the first dielectric layer, and the second metal pad is bonded to the first metal pad. In some embodiments, the recesses are portions of a recess ring encircling the first metal pad in a top view. In some embodiments, the selectively etching is a wet etching process. In some embodiments, an etchant of the wet etching process includes a mixture of sulfinylbis and hydroxylamine. In some embodiments, the selectively etching also forms a dishing profile at a middle portion of the first metal pad. In some embodiments, after the bonding a void is formed between the dishing profile of the first metal pad and the second metal pad. In some embodiments, a size of the second metal pad is larger than a size of the first metal pad, and after the bonding the recesses are capped by the second metal pad. In some embodiments, a width of the recesses ranges from about 50 nm to about 300 nm, and a depth of the recesses ranges from about 50 nm to about 300 nm. In some embodiments, the method further includes selectively etching the second metal pad to form recesses at an edge portion of the second metal pad. In some embodiments, after the bonding the recesses at the edge portion of the first metal pad are merged with the recesses at the edge portion of the second metal pad.
In another exemplary aspect, the present disclosure is directed to a method. The method includes forming a first device structure, forming a second device structure, and bonding the second device structure to the first device structure. In some embodiments, the forming of the first device structure includes depositing a first dielectric layer, forming a first metal pad in the first dielectric layer, and selectively etching an edge portion of the first metal pad to form a first recess. In some embodiments, the forming of the second device structure includes depositing a second dielectric layer, forming a second metal pad in the second dielectric layer, and selectively etching an edge portion of the second metal pad to form a second recess. In some embodiments, the second metal pad is bonded to the first metal pad and the second dielectric layer is bonded to the first dielectric layer. In some embodiments, the second metal pad is larger than the first metal pad, and the first recess is separated from the second recess. In some embodiments, after the bonding the first recess is merged with the second recess. In some embodiments, after the bonding a top surface of the first metal pad and a top surface of the second metal pad form a void therebetween. In some embodiments, the first metal pad includes a barrier layer and a metallic material surrounded by the barrier layer, and after the selectively etching a top surface of the barrier layer is substantially coplanar with a top surface of the first dielectric layer. In some embodiments, the forming of the first device structure further includes forming a first dummy metal pad in the first dielectric layer, the forming of the second device structure further includes forming a second dummy metal pad in the second dielectric layer, and after the bonding the second dummy metal pad is bonded to the first dummy metal pad with a recess ring encircling the bonded first and second dummy metal pads in a top view. In some embodiments, the bonding includes an anneal that reduces sizes of the first recess and the second recess.
In yet another exemplary aspect, the present disclosure is directed to a semiconductor device. The semiconductor device includes a first device structure and a second device structure. In some embodiments, the first device structure includes a first dielectric layer, a first metal pad in the first dielectric layer, and a first void at an edge portion of the first metal pad. In some embodiments, the second device structure includes a second dielectric layer in contact with the first dielectric layer, a second metal pad in the second dielectric layer and in contact with the first metal pad, and a second void at an edge portion of the second metal pad. In some embodiments, the first void is connected with the second void in forming a void ring encircling the first and second metal pads. In some embodiments, the second metal pad is larger than the first metal pad, and the second void is larger than the first void.
The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure.
Claims
1. A method comprising:
- depositing a first dielectric layer on a first substrate of a first device die;
- etching the first dielectric layer to form a trench;
- depositing a metallic material in the trench and on a top surface of the first dielectric layer;
- performing a chemical mechanical polish (CMP) process to remove a portion of the metallic material from the top surface of the first dielectric layer, wherein a remaining portion of the metallic material in the trench forms a first metal pad;
- after the performing of the CMP process, selectively etching the first metal pad to form recesses at an edge portion of the first metal pad;
- depositing a second dielectric layer on a second substrate of a second device die;
- forming a second metal pad in the second dielectric layer; and
- bonding the second device die to the first device die, wherein the second dielectric layer is bonded to the first dielectric layer, and the second metal pad is bonded to the first metal pad.
2. The method of claim 1, wherein the recesses are portions of a recess ring encircling the first metal pad in a top view.
3. The method of claim 1, wherein the selectively etching is a wet etching process.
4. The method of claim 3, wherein an etchant of the wet etching process includes a mixture of sulfinylbis and hydroxylamine.
5. The method of claim 1, wherein the selectively etching also forms a dishing profile at a middle portion of the first metal pad.
6. The method of claim 5, wherein after the bonding a void is formed between the dishing profile of the first metal pad and the second metal pad.
7. The method of claim 1, wherein a size of the second metal pad is larger than a size of the first metal pad, and after the bonding the recesses are capped by the second metal pad.
8. The method of claim 1, wherein a width of the recesses ranges from about 50 nm to about 300 nm, and a depth of the recesses ranges from about 50 nm to about 300 nm.
9. The method of claim 1, further comprising:
- selectively etching the second metal pad to form recesses at an edge portion of the second metal pad.
10. The method of claim 9, wherein after the bonding the recesses at the edge portion of the first metal pad are merged with the recesses at the edge portion of the second metal pad.
11. A method comprising:
- forming a first device structure comprising: depositing a first dielectric layer; forming a first metal pad in the first dielectric layer; and selectively etching an edge portion of the first metal pad to form a first recess;
- forming a second device structure comprising: depositing a second dielectric layer; forming a second metal pad in the second dielectric layer; and selectively etching an edge portion of the second metal pad to form a second recess; and
- bonding the second device structure to the first device structure, wherein the second metal pad is bonded to the first metal pad and the second dielectric layer is bonded to the first dielectric layer.
12. The method of claim 11, wherein the second metal pad is larger than the first metal pad, and the first recess is separated from the second recess.
13. The method of claim 11, wherein after the bonding the first recess is merged with the second recess.
14. The method of claim 11, wherein after the bonding a top surface of the first metal pad and a top surface of the second metal pad form a void therebetween.
15. The method of claim 11, wherein the first metal pad includes a barrier layer and a metallic material surrounded by the barrier layer, and after the selectively etching a top surface of the barrier layer is substantially coplanar with a top surface of the first dielectric layer.
16. The method of claim 11, wherein the forming of the first device structure further includes forming a first dummy metal pad in the first dielectric layer, the forming of the second device structure further includes forming a second dummy metal pad in the second dielectric layer, and after the bonding the second dummy metal pad is bonded to the first dummy metal pad with a recess ring encircling the bonded first and second dummy metal pads in a top view.
17. The method of claim 11, wherein the bonding includes an anneal that reduces sizes of the first recess and the second recess.
18. A semiconductor device comprising:
- a first device structure comprising: a first dielectric layer; a first metal pad in the first dielectric layer; and a first void at an edge portion of the first metal pad; and
- a second device structure comprising: a second dielectric layer in contact with the first dielectric layer; a second metal pad in the second dielectric layer and in contact with the first metal pad; and a second void at an edge portion of the second metal pad.
19. The semiconductor device of claim 18, wherein the first void is connected with the second void in forming a void ring encircling the first and second metal pads.
20. The semiconductor device of claim 18, wherein the second metal pad is larger than the first metal pad, and the second void is larger than the first void.
Type: Application
Filed: Jan 26, 2023
Publication Date: Jan 4, 2024
Inventors: SyuFong LI (Taoyuan), Yu-Ping TSENG (Taipei City), Li-Hsien HUANG (Hsinchu County), Yao-Chun Chuang (Hsinchu City), Yinlung LU (Hsinchu)
Application Number: 18/159,938